Dynamic deposition behavior of supramolecular hydrogels loaded with thifluzamide on rice leaves

The surface of rice leaves is covered with villi, papillae, wax and other special structures, and there is a certain dip angle of rice leaves. Pesticide spray droplets can easily bounce off the leaf surface, pollute soil and groundwater, and futher cause serious harm to non-target organisms. Therefore, improving the retention and deposition of pesticide spray droplets on rice leaves is essential for improving the effective utilization of pesticides. In this work, folic acid and zinc nitrate were used as raw materials to design a folate/Zn²⁺ supramolecular hydrogel loaded with thifluzamide, which had the advantages of biocompatibility and biodegradability. And the raw materials was rich in source, and the preparation process of the hydrogel was simple and easy to operate. Folic acid is a water-soluble vitamin-B whose parent compound consists of a combination of teropterin, p-aminobenzoic acid and glutamate. The folic acid molecule formed a tetramer through the pteridine part, and then combined with Zn²⁺. The gel was cross-linked to form a nanofiber network structure. The rheological properties of the folate/Zn²⁺ supramolecular hydrogel loaded with thifluzamide was measured by a rheometer, which suggested that the ratio of folic acid and zinc nitrate could affect the mechanical strength of the prepared gel and higher ratio of zinc ions was associated with stronger mechanical strength of the formed gel. In addition, the gel prepared with the ratio of folic acid and Zn²⁺ in the range of 1/1.8-1/2.0 was suitable for pesticide spraying, which had the characteristics of shear-thinning and self-healing. And the folate/Zn²⁺ supramolecular hydrogel loaded with thifluzamide was used to study the deposition behavior of droplets on rice leaves by ultra-high-speed photography. The results showed the gel droplets can stably deposit on the surface of superhydrophobic rice leaves without bouncing, fragmentation and splashing phenomena.